Microsoft IIS Connection Strings Decryption

Detects use of aspnet_regiis to decrypt Microsoft IIS connection strings. An attacker with Microsoft IIS web server access via a webshell or alike can decrypt and dump any hardcoded connection strings, such as the MSSQL service account password using aspnet_regiis command.

Sigma rule (View on GitHub)

 1title: Microsoft IIS Connection Strings Decryption
 2id: 97dbf6e2-e436-44d8-abee-4261b24d3e41
 3status: test
 4description: Detects use of aspnet_regiis to decrypt Microsoft IIS connection strings. An attacker with Microsoft IIS web server access via a webshell or alike can decrypt and dump any hardcoded connection strings, such as the MSSQL service account password using aspnet_regiis command.
 5references:
 6    - https://www.elastic.co/guide/en/security/current/microsoft-iis-connection-strings-decryption.html
 7author: Tim Rauch, Elastic (idea)
 8date: 2022/09/28
 9modified: 2022/12/30
10tags:
11    - attack.credential_access
12    - attack.t1003
13logsource:
14    category: process_creation
15    product: windows
16detection:
17    selection_name:
18        - Image|endswith: '\aspnet_regiis.exe'
19        - OriginalFileName: 'aspnet_regiis.exe'
20    selection_args:
21        CommandLine|contains|all:
22            - 'connectionStrings'
23            - ' -pdf'
24    condition: all of selection*
25falsepositives:
26    - Unknown
27level: high

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